Andersox



E. F. W. ALEXANDERSON.

memo SYSTEM or SHIP PRoPuLsloN.

Awucmdn mpio ma. 2z. me.

Patented May 20, 19M).

Inventor: Ernst, Wflexanderson be C4/M 32W;

His JTttorneg UNITED STATES PATENT oEEIoE.

ERNST r. W. ALExANDEnsoN, or SCHENECTADY, NEW YORK, AssiGNoE To GENERAL .ELECTRIC COMPANY, A CORPORATION or NEW YORK.

Spccication ot Letters Patent.

Patented May 20, 1919.

Application led March 22; 1916. Serial No. 86,013.

To all whom it may concern Be it known that I, ERNST F. Vif. ALEX- ANDEnsoN, a citizen of the United States, residing at Schenectady, county of Schenee tady, State of New York, have invented certain new and useful Improvements in Electric Systems of Ship Propulsion, of which the following is a s ecification.

My invention re ates to ship propulsion and particularly to systems of ship propul- Asion in which the ships propeller-s are driven by electric motors. The object of the invention is to provide an improvcd'electric system of ship propulsion. Other objects of tle invention will be particularly pointed out in the course of the following description.

The system of my present invention is particularly adapted for equipments in which it is necessary that the propelling apparatus operate economically at two different speed ranges. Take, for examle, the case of a battleship, where hio'h e ciency at a high range-of speeds and at a lower range of speeds is particularly essential, and in fact practically necessary. In such ships, economic operation of the propelling apparatus must be o tained over the desired range of high Speeds, including full speed, and also over a suitable range of lower speeds, which I will term the cruising speeds: The present invention more particularly relates to electric systems of ship propulsion in which electric energy is applied to propeller-driving induction motors by turbine-driven alternators. Speed variations of a Ship )ropelled by such a system can be obtaine by varyino the admission of operating Huid to the tur ines, but eiiicient operation over such a wide range of speeds as would include both the high and cruising speeds of the ship can not be satisfactorily obtained merely by varying the steam admission to the turbines, since if a turbine is designed and proportioned for `high efficiency at its high speeds,- its efficiency will be much poorer at theV relatively low speeds corresponding to the cruising speeds of the ship. The power required to propel a vessel `varie-a approximately as the cube of her speed,'xand, accordingly. at cruising speeds considerably less than the maximum power of thi propelling equipment is required for drivingtlie ship, and greater economy could be obtained by using a small high pressure turbine operating ata higher speed in series with the main turbine, which in such a case would be sed as a low pressure turbine. The diliicultyfin practically employing such a system lies in the fact ythat the full speed of the main turbineis such that a two-pole generator must be used, and, therefore. it is not possible to use a generator of the ordinary kind with the high pressure cruising turbine, since the speed of thel latter should be higher than that of the main turbine for this condition of operation. William L. ll. Emmet has described in an application for Letteis Patent of thc'Uniled States. Serial No. 84,490, filed March 15. 1916, an urrnngxx ment of apparatus by which tw-o turbines operating in scri-ss can be operatively connected to two electric generatois so that the latter may operate in parallel to supply electric energy to a prolwller-driring induction motor. In its complete form thc llunnct arrangement comprises a synchronous` generator und an induction generator so connected to the main and cruising turbines that a rc- ]ation is esbiblishcd bctwccn thc turbinesl whereby the auxiliary turbine can operato at a higher spoed than the main turbine and at the same time the two generators can be electrically connected to supply energy in parallel to the propcllcidriving induction motor. Ii in the Emmet arrangement thc induction generator is mechanically independent of the main turbiml und is drircn sorely by the auxiliary turbine, spia-traducing gearing must be interposed bolwccn thc auxiliary turbine and the induction gcncrator. The particular aim of my present invention is to provide an improved system of this general character in which the two gcnerators can be directly coupled lo their respective prime movers, und still more particularly the aim of my present invention is to enable the use of two direct-connected turbo-generators` of the syiwhronous typo in asystcni of this clmractor, und io this and l propose to employ an ordinary synchronomA generator and a double synchronous generator in place of the synchronousl and induction generatois, respectively, ol' thc Emmi-l arrangement.

The novel vfeatures which l believe to be patentabiy chamctcristic of my invention are definitely pointed out in the claims appended hereto. Thearrangement of the apparatus in and the mode of operation of the ,system of my presentinvention will be best understood from the following description taken in conjunction with the accompanyingr drawing, in which:

The figure diagraniniatically represents an electric system of ship propulsion embodyin r my present invention.

n the drawings there is diagraminatically represented a main elastic-fluid turbine 5 designed for high etliciency asa high-speed high-pressure machine and ada )ted for economic operation at llower speer s ywhen supplied witli -elastic-fluid of lower pressure. The main turbine is directly coupled to an alternating current generator 6. erator 6 is preferably a polyphase synchronous alternator of .the revolving field type. The generator G is electrically connected by means of leads 7 to a polyphase induction motor 8. The rotor of the induction motor is mounted on a propeller shaft 9, carrying a propeller 10.

An auxiliary or cruising turbine 11, designed for high eliiciency as a high-speed high-pressure machine, has its exhaust 12 connected to 'the admission I3 of the main turbine 5. The admission 14 of the auxiliary turbine is connected to the main supply pipe 1f) connnunnicating with a suitable source of elastic fluid, such, for example, as the steam boilers of the ship. The main supply pi )e 15 is also in communication with the admission 13 of the main turbine 5. Three valves 16, 17 and 18 are shown for controlling the steam admission to the turbines 5 and 11. 'hen valves 1G and 1S are closed and valve 17 open, the main turbine 5 receives steam directly from the boilers and its exhaust 1S) may he connected to a suitable condenser, as well understood. Under this condition of operation the main turbine will run at high speeds with high elliciency, and variations of the ships speed over the highspeed range can he obtained by varyingvthe steam admission to the turbine, whereby the speed of the turbine and. accordingly the frequency of the alternating current energy delivered to the` propeller-driving induction motors are correspondingly varied. v

The rotin-.of the auxiliary turbine 11 lis directly coupled to the rotor 31 of a doubles),'nchronous gencmtor. The rotor`31 carries a polyphase field winding 32 connected to slip rings 33. The stator 3l ofthe doublesynchronous generator carries :'i polyphase armature windingr 35 which is substimtially a counterpart of the polypliase field winding 32. The armature and field windings 35 and 32 are designed to be connected in parallel by means of a synchronizing 'switch 3G and to the leads 7 by means of a switch 24. When the fichi windinlgl 32 is excitedwith alternating current a rotating magnetic field is produced, and if under such circumstances the rotor 31 is driven at twice synchronous` The genspeed with reference to the frequency of the exciting current, an alternating current of the same frequency as the exciting current will be induced in the armature winding In other words since the field of the generator is itself rotating at synchronous speed the field magnet structure must be rotated at double synchronous speed.

The propeller-driving induction motor 8 is mechanically independent of the main and auxiliary turbines, wherefore the propeller 10 is driven by a torque developed entirely by this motor. It will of course be understood that more'. than one propeller-driving motor may be coupled to each propeller shaft. A reversing switch 25 is provided for mitting high-pressure steam to'tthe main turbine Tlie inain turbine 5 and generator 6 thus run at their respective high speeds l,and the frequency of the alternating current energy delivered by tlie generator (i to the induction'niotor 8 issuch .as Vto produce the proper propeller speed for high speed navigat-ion of the Shiip. During this condition of operation the auxiliary turbine 11 and the doiible-synchronous generator are o )eratively inactive and remain at rest. 'Slpeed variations ofthe propeller and hence of the ship t'or this condition of operation can be obtained by controlling the admission of steam to the turbine 5, and for this purpose a valve 42 is included in the main supply pipe 15. The valve 42 is designed to be operatively connected to a speed governor on the main turbine 5 and to a suitable speed control lever, substantially as described in United States Letters Patent granted to lV. Ehunet, No. 1,137,308, dated April 27,

For the navigation of the ship at the lower range of speeds, such as her cruising speeds, the two turbines are connected in series. This condition of operation is obtained by closing the switch 24 and Avalve ,17, and opening" valyfes 16 and 18, whereby the two generators are electrically connected together and high-pressure steam is admitted. drcetly tothe'cruising turbine 11, while the main turbin operates with exhaust steam received from Athecil'uising turbine. The

rclative'spceds of tl'ietiirbines 5 andl 11 will this speed relation between the turbines the two generators must be synchronized, and this can be donc by bringing the double- Isynchronous generator up to a speed slightly higher than double synchronism and then permitting this generator to slow down.`

lli en the speed of the double-synchronous generator falls to double synchronism the field synchronizing switch 36 can be closed and the two generators will fall into step and will thereu )on definitely establish the relative Speedso the turbines. Any suitable synchronisrn' indicator, such as the lam 37, may be shunted around the synchronizing switch 36. Durin the act of synchronizing, the main turbine 5 will be loaded to a greater or less extent, while the cruising turbine 11 will be running light, and thus no diiiculty will be encountered in bringing the erusin turbine up toa speed slightly renter than ouble synchronism. It will t us be evident that the synchronous and doublesynchronous generators establish a relation between the main and cruising turbines such that the latter can run at double synchronous speed while theformer runs at synchronous speed, and at the same time the two generators are operating in parallel to supply electric energy to thepropeller-driving motor or motors. lVhen the double erator falls into step at dou le synehronism with .the synchronous generator 6, the two generatorsI become electrically locked in step', as well understood in the art, and a definite speed relation between the two turbines is tiereby established and maintained Within the limits of the electro-dynamic capacity of the two generators.

For the purposes ot' explanation I will assume that the full speed of the main turbine 5 is 2200 R. I. M., and that this speed of tho main turbine will drive the ship at 35 knots per hour. I will also assume that the full speed of the cruising turbine 11 is 3600 R. P. M., so that when the cruising and main turbines are connected in series the speed of the main turbine will be 1800 R. P. M., assuming the generators to be bi-polar. For speeds between 35 and about 28 knots the main turbine will be operated alone, and speed variations over thls speed range can be obtained by varying the steam admission to the turbine. For speeds below about 28 knots the two turbines will be connected in series and the two generators will supply electric energy in parallel to the propellerdriving motor or motors. Variations. in speed for this arrangement of the apparatus will be obtained by varying the admission of livel steam to the crusing turbine. If a still lower range of speeds is necessary the motor 8 can be provided with a primary Winding adapted to produce primary magnetic poles of different polc numbers. Any suitable arrangementof the primary winding for polenchronous genchanging can be employed, and I have shown in the accompanying drawing a pole-changing switch 38 for this purpose. Thus for speeds below about22 knots the pole-changing switch 38 will be moved to its low-speed position, whereby the primary winding of the motor 8 is arranged to produce its higher number of primary poles. Where such large speed variations are not necessary, economical operation over a reasonable range f speeds can be obtained by using the main turbine alone at the higher speeds, and the two turbines in series and the "enerators in parallel at the lower s eeds with only one pole combination of tie propeller-driving motors.

The auxiliary turbine 11 has a speedlilniting device or governor operatively connected to a valve 41 in the steam supply pipe thereof. The governor and valve are designed to limit the speed of the turbine 11, so as to prevent the speed of this turbine rising above a predetermined value. The governor and valve 41 may advantageously be of that type described in the United States Letters Patent of lV. L. R. Emmet, No. 1,137,593, dated April 27, 1915.

The double-synchronous generator has a very special usefulness in a system of the character herein described. As previously mentioned, in order to get proper motor conditions in ship propulsion, it is generally necessary to use a low electrical frequency, and such low frequency makes ditiicult the application of a cruising turbine of sutliciently high speed. The double-synchronous generator enables the use of the advantageous hig -speed cruising turbine without necessitating speed reducing gearing and clutches, both of which devices are more or less objectionable for'such purposes. Furthermore, the double-synchronous generator is of relatively small size, andsince its magnetization is furnished by the main generator no additional exciters are needed. Another particular advantage of this arrangement is that such a cruising turbine and double-synchronous generator combination can be used in connection with any one of a plurality of main turbine generating units.

lfVhat I claim as new and desire to secure by Letters Patent of the United States, is,-

1. An electric system of ship propulsion comprising a main elastic-fluid turbine, a synchronous alternator coupled to said turbine, an auxiliary elastic-fluid turbine, means for supplying the exhaust Huid of said auxiliary turbine to the admission of said main turbine, a double-synchronous alternator coupled to said auxiliary turbine, a propeller, an electric motor operatively connected to said propeller, and means for electrically connecting said two alternators so that they deliver electric energy in parallel to said motor, said tw alternators being electrically so proportioned as to establish a relation between the turbines whereby the auxiliary turbine operates at a higher speed than the lnain turbine.

2. An electric system of ship propulsion comprising a main elastic-'fluid turbine, an alternating current generator coupled to said turbine, an auxiliary elastic-iiuid turbine, means for supplying the exhaust Huid of said auxiliary turbine to the admission of said main turbine, a second alternating current generator coupled to said auxiliary turbine, said second .alternatin current generator being adapted for para lel operation with' said first-mentioned generator when driven at double synchronism, a propeller, an electric motor operatively connected to said propeller, and means for electrically connecting said two generators so that they deliver electric energy in parallel to said motor, said two generators being electrically proportioned to establish a relation between the turbines whereby the auxiliary turbine operates at a higher speed than the main turbine.

3. An electric System of ship propulsion comprising a propeller, an electric motor operatively connected to said propeller, a main alternating current generator adapted to deliver electric energy to said motor, a main elastic-fluid turbine coupled to said generator, a double-synclironous alternating current generator also adapted to deliver electric energy` to said motor, an auxiliary elasticfluid turbine operatively connected to said double-synchronous generator, and

means for supplying elastic-Huid to said main turbine while the auxiliaryv turbine remains operatively inactive for high speed navigation of the ship and for supplying the exhaust Huid of vsaid auxiliary turbine to said main turbine and electrically; coni necting said generators in parallel w reby the main turbine runs at a lower speed than the auxiliary turbine and electric energy is supplied from both generators to said motor for navigating the ship at lower speeds.

4. An electric system of ship propulsion comprisingl ainain elastic-Huid turbine, a. synchronous alternating current generator coupled to said turbine, a double-synchronous alternating current generator, an auxiliary elastic-fluid turbine coupled to said -double-synchronous generator, a propeller,

an electric motor operatively connecteaiy to said propeller and adapted to receive electric energy from each of said generators,

and means for operating said main turbine and said synchronous generator at their respective high speeds by admitting elastic fluid direct to the main turbine for high speed navigation of the ship -and for operating -said main turbine and smid synchronous generator at relatively lower speeds by supplying the exhaust Huid of, said auxiliar turbine to said main turbine and electrica ly connecting said generators i:

in parallel for navigating the ship at relatively lower sueeds.

In witness whereof 1 have hereunto set my hand this 21st day of March, 1916.

ERNST F. W. ALEXANDERS( 1N 

